Recently, heat-shrinkable plastic films have widely been used aiming at wrapping of packaged articles for improvement in appearance, at packaging for avoiding direct impact of contents, and at label package serving as protection of glass bottles or plastic bottles and display of articles. In plastic materials used for these purposes, are drawn films, such as polyvinyl chloride films, polystyrene films, and the films are used for labels, cap seals, or integrated packaging, for various containers, such as polyethyleneterephthalate (PET) containers, polyethylene containers, and glassware.
However, on one hand, polyvinyl chloride films have outstanding shrink characteristics, but have low heat-resisting property. Furthermore, it has problems of generation of hydrogen chloride gas or dioxins in incineration. In addition, use as shrink labels of heat-shrinkable vinyl chloride resin films for, such as PET containers, causes a problem of needing separation of the labels from the containers, in recycling use of the containers.
On the other hand, polystyrene films enable separation based on specific gravities difference between the films and PET bottle containers, and they also has outstanding quality after shrink-finishing (for example, patent document 1). In addition, polyester films have outstanding solvent resistance, do not generate black smoke or off-flavor in incineration, and, as a result, they may exhibit outstanding properties with respect to environmental problems. However, in selling with vending machines of final products, with use of these films as labels for PET bottles, unsatisfactory slipping property of a label surface may induce jamming when supplying of final products to the vending machine, or discharging of the final products therefrom. There have occurred problems that especially the final products may not be passed through a passage for the products, and may not be conveyed to an exit, inducing multiple discharges of the products. There exists necessity for improvement of these problems.
Patent document 1: Japanese Patent Laid-Open No. 2002-108217
In actual use of the heat shrinkable films in covering of containers, printing is performed thereonto, if needed, and, subsequently they are processed into shapes of labels (cylindrical labels), inner tubes, bags, etc. And after wrapping with the processed film of containers, the containers, on conveyor belts etc., pass through tunnels such as a steam tunnel (a shrinking tunnel system wherein heated steam is blown in for heat shrinking), or a hot air tunnel (a shrinking tunnel system wherein heated air is blown in for heat shrinking) to shrink the processed film and to tightly attach on the containers.
Steam tunnels can exhibit more excellent efficiency of heat transfer as compared with hot air tunnels, and can give more uniform heat shrinkage, and therefore may easily provide more excellent appearance after shrink-finishing as compared with hot air tunnels. However, in case of addition of wax components in order to provide, for example, slipping property with a resin constituting the film, there may occur such a problem that the wax components in the film surface may be removed by steam blown for heat shrinking within the steam tunnel to deteriorate the slipping property of the shrinking label.
In addition, for improving slipping property there has been adopted a method of applying a layer having excellent slipping property on a film surface. (For example, patent document 2) However, the method is performed by post processing of the film, has a problem in processing costs, and it wears by friction between rolls and laminated layers outside in processing, resulting in problems of decrease in productivity. In addition, application of easily-slipping coating for giving slipping property to a film surface before printing or after printing may deteriorate solvent adhesion property, and thereby deterioration of solvent adhesion property may sometimes cause exfoliation of an adhered area in heat shrink process, disabling solvent adhesion in an extreme case.
Patent document 2: Japanese Patent Laid-Open No. 2002-196677